feat(connection): add listCollections() helper to connections

lib/connection.js

@@ -605,6 +605,26 @@ Connection.prototype.dropCollection = async function dropCollection(collection)
   return this.db.dropCollection(collection);
 };
 
+/**
+ * Helper for MongoDB Node driver's `listCollections()`.
+ * Returns an array of collection objects.
+ *
+ * @method listCollections
+ * @return {Promise<Collection[]>}
+ * @api public
+ */
+
+Connection.prototype.listCollections = async function listCollections() {
+  if ((this.readyState === STATES.connecting || this.readyState === STATES.disconnected) && this._shouldBufferCommands()) {
+    await new Promise(resolve => {
+      this._queue.push({ fn: resolve });
+    });
+  }
+
+  const cursor = this.db.listCollections();
+  return await cursor.toArray();
+};
+
 /**
  * Helper for `dropDatabase()`. Deletes the given database, including all
  * collections, documents, and indexes.

test/connection.test.js

@@ -94,7 +94,7 @@ describe('connections:', function() {
       }));
       await Model.init();
 
-      const res = await conn.db.listCollections().toArray();
+      const res = await conn.listCollections();
       assert.ok(!res.map(c => c.name).includes('gh8814_Conn'));
       await conn.close();
     });
@@ -185,16 +185,25 @@ describe('connections:', function() {
         size: 1024
       });
 
-      const collections = await conn.db.listCollections().toArray();
+      const collections = await conn.listCollections();
 
       const names = collections.map(function(c) { return c.name; });
       assert.ok(names.indexOf('gh5712') !== -1);
       assert.ok(collections[names.indexOf('gh5712')].options.capped);
       await conn.createCollection('gh5712_0');
-      const collectionsAfterCreation = await conn.db.listCollections().toArray();
+      const collectionsAfterCreation = await conn.listCollections();
       const newCollectionsNames = collectionsAfterCreation.map(function(c) { return c.name; });
       assert.ok(newCollectionsNames.indexOf('gh5712') !== -1);
     });
+
+    it('listCollections()', async function() {
+      await conn.dropDatabase();
+      await conn.createCollection('test1176');
+      await conn.createCollection('test94112');
+
+      const collections = await conn.listCollections();
+      assert.deepStrictEqual(collections.map(coll => coll.name).sort(), ['test1176', 'test94112']);
+    });
   });
 
   it('should allow closing a closed connection', async function() {

test/types/connection.test.ts

@@ -70,6 +70,10 @@ expectType<Connection>(conn.useDb('test', {}));
 expectType<Connection>(conn.useDb('test', { noListener: true }));
 expectType<Connection>(conn.useDb('test', { useCache: true }));
 
+expectType<Promise<string[]>>(
+  conn.listCollections().then(collections => collections.map(coll => coll.name))
+);
+
 export function autoTypedModelConnection() {
   const AutoTypedSchema = autoTypedSchema();
   const AutoTypedModel = connection.model('AutoTypeModelConnection', AutoTypedSchema);

types/connection.d.ts

@@ -121,6 +121,12 @@ declare module 'mongoose' {
      */
     readonly id: number;
 
+    /**
+     * Helper for MongoDB Node driver's `listCollections()`.
+     * Returns an array of collection names.
+     */
+    listCollections(): Promise<Pick<mongodb.CollectionInfo, 'name' | 'type'>[]>;
+
     /**
      * A [POJO](https://masteringjs.io/tutorials/fundamentals/pojo) containing
      * a map from model names to models. Contains all models that have been